Field of the Invention
The invention relates to a circuit-breaker such as those used in power plants, transformer substations and other installations in the supply of electric energy for connecting and disconnecting operating currents and overcurrents.
Discussion of Background
Circuit-breakers of the generic type have long been known in which the arc struck during an opening operation between the contact members is extinguished by extinguishing gas from a pressure volume. The pressure is produced in this case by a piston which is driven simultaneously with the second contact member by a switching drive, or is even formed by a part of the same, see DE-A-196 13 568, for example. However, as a result the switching drive is exposed to a high load which requires the same to be generously dimensioned. This naturally has an effect on the production costs of the circuit-breaker.
EP-B-0 548 390 and U.S. Pat. No. 4,617,436 have also disclosed switching devices in which use is made in the switching drive of charges of explosive which are ignited in order to trigger an opening operation. The gas produced during the explosion acts on a piston which is operationally connected to a movable contact member and drives the same into the open position under the action of the gas pressure. The gases produced during the explosion are, however, kept away from the contact members and not used for blowing out an arc possibly drawn between the same.
Also known are fuses in which an electric connection is severed by the explosion of an explosive charge. DE-A-35 37 314 describes such a fuse with a tubular bridge conductor which is centrally constricted and surrounded by a pressure chamber and on whose outside an explosive charge is fitted circumferentially in the pressure chamber. The pressure chamber is lined with a material which, after ignition of the explosive charge and blasting of the bridge conductor emits, under the influence of a forming arc, electro-negative gas. The electro-negative gas forms, together with the gases produced by the explosion, a highly pressurized extinguishing gas which flows off into an expansion chamber while blowing out the arc. Use in fuses of powders which form extinguishing gas is also known from EP-A-0 657 910 and EP-A-0 641 005.
However, fuses must be at least partially replaced after a single opening operation. In the case of that described in DE-A-35 37 314, not only is the explosive charge consumed and the bridge conductor destroyed, but the extinguishing gas is additionally essentially produced by the action of the arc on the lining of the pressure chamber, which is likewise used up in this case. Moreover, a time delay which is not conducive to an effective blowout operation may result between the production of the highly pressurized explosion gases and the flow chiefly triggered by them and the emission of electro-negative gas not triggered until the arc occurs.